1. Field of the Invention
The present invention relates to a sheet discharge apparatus for discharging a cut sheet (referred to as merely "sheet" hereinafter) on which an image was formed, and an image forming apparatus such as a copying machine, a printer, a facsimile and the like having such a sheet discharge apparatus, and more particularly, it relates to a sheet discharge apparatus wherein a sheet on which an image was formed in a face-down manner is discharged in a face-down manner or a face-up manner after inversion, and an image forming apparatus having such a sheet discharge apparatus.
2. Related Background Art
In the past, in sheet discharge apparatuses used with image forming apparatuses such as printers, face-down discharge (FIG. 9) in which a sheet on which an image was formed is discharged with an imaged surface thereof facing downwardly or face-up discharge (FIG. 10) in which a sheet on which an image was formed is discharged with an imaged surface thereof facing upwardly is adopted.
As shown in FIG. 9, in a printer having a face-down sheet discharge apparatus, sheets are supplied one by one from a sheet cassette 2 to an image forming portion 4 by means of a sheet supply roller 3, and an image is formed on an upper surface of the sheet in the image forming portion. The sheet S on which the image was formed is inverted by a pair of discharge rollers 5 and a reverse rotation guide 6 and then is discharged onto a sheet stacking portion 9 through a pair of rollers 7 with the imaged surface A facing downwardly. The face-down discharge method is particularly useful for compact printers since the imaged sheets can be stacked in a page sequence and the discharge sheet stacking portion 9 can be formed on a body 8 of the printer to save installation space.
On the other hand, as shown in FIG. 10, in a printer having a face-up sheet discharge apparatus, the sheet S on which the image was formed in the image forming portion 4 in the same manner is discharged onto a sheet stacking tray 10 through the pair of discharge rollers 5 with the imaged surface A facing upwardly. Although this face-up discharge method cannot save installation space since the sheet stacking tray protrudes laterally from the printer body 8, the imaged information on the sheet can easily be ascertained since the sheet is discharged with the imaged surface A facing upwardly.
In consideration of the above, as shown in FIG. 11, there has been proposed a sheet discharge apparatus 11 wherein the face-down discharge and the face-up discharge can be switched. In this sheet discharge apparatus, a switching guide 12 is disposed at a downstream side of the pair of discharge rollers 5 and can be rotated around a fulcrum 12a by a predetermined amount by means of an operation lever or an actuator such as a solenoid. With this arrangement, the imaged sheet discharged through the discharge rollers 5 can selectively be directed toward the reverse rotation guide 6 or toward the sheet stacking tray 10. FIG. 12 shows a condition that the switching guide 12 is switched to direct the sheet toward the tray 10. In this case, the sheet S discharged through the discharge rollers 5 is discharged onto the sheet stacking tray 10 with the imaged surface A facing upwardly (face-up discharge). On the other hand, FIG. 13 shows a condition that the switching guide 12 is switched to direct the sheet toward the reverse rotation guide 6. In this case, the sheet S discharged through the discharge rollers 5 is discharged onto the sheet stacking portion 9 through the reverse rotation guide 6 and the pair of rollers 7 with the imaged surface A facing downwardly (face-down discharge).
Further, as shown in FIGS. 14A and 14B, there has also been proposed a sheet discharge apparatus wherein a side plate 33 is pivotally mounted on a support pin 34 and a switching guide 32 is pivotally mounted on an upper portion of the side plate via a pin 35.
In this sheet discharge apparatus, as shown in FIG. 14A, under a condition that the switching guide 32 is folded with respect to the side plate 33 and the side plate 33 is closed, the sheet discharged through the discharge rollers 5 is guided by a reverse rotation surface 32a formed on the switching guide to be discharged onto the sheet stacking portion 9 in the face-down manner. On the other hand, as shown in FIG. 14B, under a condition that the side plate 33 is opened and the switching guide 32 is rotated with respect to the side plate 33, the sheet discharged through the discharge rollers 5 is guided by a tray surface 33a formed on the side plate 33 and a tray surface 32a formed on the switching guide 32 and is discharged in the face-up manner.
However, the sheet discharge apparatus having the switching guide requires the switching guide 12 and the operation lever or the actuator for driving the switching guide, thereby making the printer complex, and, due to the presence of the switching guide, the occurrence of sheet jam will be increased. Further, since it is difficult for the operator to judge whether the switching guide 12 is switched to direct the sheet toward the tray or the reverse rotation guide, malfunction will easily occur (for example, the operator erroneously selects the face-down mode in place of the face-up mode or vice versa).
Further, when the apparatus is made compact by adopting the face-down sheet discharge, although it is necessary to dismount the sheet stacking tray from the apparatus and to preserve it anywhere, a new reserving space for the dismounted sheet stacking tray is required, and there is a danger of misplacing the sheet stacking tray. Further, since there is the switching guide 12 within the apparatus, if the sheet is jammed in the proximity of the discharge rollers 5, it is difficult to remove the jammed sheet due to the presence of the switching guide 12. In addition, when the path is switched to prevent the sheet from being caught, since the accurate rocking angle of the switching guide 12 is required, it takes a long time to assemble the apparatus.
On the other hand, in the conventional apparatus shown in FIGS. 14A and 14B, since the switching guide 32 can be extended out of the apparatus, the jammed sheet can easily be removed. However, in this case, since the guide surface 32a is exposed, the guide surface 32a may be damaged.
Incidentally, the above problems arise in the image forming apparatus having one of the above mentioned sheet discharge apparatus.